Method for rendering cellulosic materials fire resistant



Patented Feb. 9, 1554 UNITED STATES PATENT OFFICE METHOD FOR RENDERING CELLULOSIO MATERIALS FIRE RESISTANT No Drawing. Application November 27, 1951, Serial No. 258,533

4 Claims. (01. 11762) This invention relates to a method for rendering materials fire resistant. This is a continuation-in-part of our copending application Serial No. 229,272 filed May 31, 1951. More specifically it relates to a method for rendering cellulosic materials fire resistant.

Many types of agents have been proposed for rendering cloth, paper and other fibrous materials fire resistant, and some have been successfully employed but few have the necessary prop erties to be able to withstand the rigors of handling and cleaning, particularly of washing and laundering. Some of the known treating agents are capable of being washed and laundered to a limited degree, but most of them appreciably alter the appearance, texture or tensile strength of the treatedcellulosic material. In addition many of the known agents are not sufficiently adherent and tend to separate from the treated material in the form .of fine dust.

Among the fire retarding agents which are non-launderable are the phosphate, borate and sulfamate types. Launderable types of agents include resins, chlorinated resins, or waxes added in combination with inorganic oxides such as antimony oxide. They, however, have the disadvantage of altering the appearance of the material considerably, and that they must be added in large quantity. Titanium has been added in several fire resistant processes, but in most of these the titanium has been added as titanium dioxide in order to obtain opaque pigment effects.

Titanium tetrachloride solutions have been tried for rendering cellulosic materials fire resistant but have met with the disadvantage that the solution is too acid and therefore has undesirable tendering effects on the cellulcsic materials. It is therefore necessary to employ titanium salt solutions which are not as strongly acid as titanium tetrachloride. It has been found that aqueous solutions. of partially substituted chlorides of tetravalent titanium may be used for rendering cellulosic materials fire re- 'sistant without tenderizing the material. Solutions which fall within the partially substituted chlorides are basic titanium chloride solutions, that is a portion of the chloride ions replaced by hydroxyl or oxidic groups (better known and sometimes referred to hereinafter as titanium oxychlorides), and titanium organo chlorides such as e. g. titanium chloride acylate solutions. It has been found that preferably from 1 to 3 of the chloride ions may be substituted by other groups including oxidic or hydroxyl groups of organic radicals. The preparation of a titanium chloride acylate solution is more particularly described and claimed in co-pending application Serial No. 229,274 filed May 31, 1951. Basic titanium chloride solutions containing small amounts of soluble phosphates are particularly desirable to employ in the process of the instant invention. These solutions are more particularly described and claimed in co-pending application Serial No. 253,973 filed October 30, 1951. In order to improve flame resistance together with resistance to afterglow it is desirable to add antimony chloride to the aqueous solution of partially substituted chloride of tetravalent titanium.

When treating cellulosic materials with these solutions according to known methods the treated material exhibits some measure of fire retardance but cannot withstand the rigors of repeated launderings. Also the appearance of the cellulosic material is changed to a dusty chalky character and the loss of the titanium values is considerable during the processing steps.

An object of this invention is to provide a process wherein cellulosic materials may be rendered fire resistant and capable of withstanding repeated washings or launderings. A further object is to provide a method for rendering cellulosic materials fire resistant which will not change the appearance or texture of such materials. A further object is to provide a method for rendering cellulosic materials fire resistant by a process which will utilize substantially all of the titanium values in said solutions. These and other objects of the present invention will become apparent as the invention is more fully described.

In its broadest aspects this invention contemplates a process for rendering cellulosic materials fire resistant by impregnating the material with an aqueous solution of partially substituted chlorides of tetravalent titanium, partially drying said solution on said material to form :a transparent gel, alkalizing the gelatinized solution retained in said material with an alkaline neutralizing agent and subsequently washing and drying said material. It is desirable to impregnate said material with an amount of solution which is equivalent to form 60% to 100% of the weight of the cellulosic material. In order to form a transparent gel on the cellulosic material by the partial drying step, it has been found that from 50% to of the Weight of the solution impregnated in the cloth should be removed. For improved flame resistance together with improved resistance to afterglow the above process maybe carried out using an aqueous solution invention includes fabrics such as cotton, linen-,1.

regenerated cellulose, viscose and. cellulose ace-- tate, also natural fibers such as kapok, hemp,

wood and wood products such as pressed boardsa.

cardboard, batting, paper, wood flour, sawdust, and the like.

The cellulosic material may be treated withtheaqueous solution of partially substituted' chlorides of tetravalent titanium by anyponvenientmeans.

such as by dipping the materialrin'th'e solution, or by spraying the solution on the material. Any excess solution on the cellulosic materialmay be removed, for example, by squeezing betweenrolla.

deliquoring in a filter press or by any other appropriate methods depending upon the physical na ture of the material employed.

As stated previously in the impregnation step. itis; preferred to leave a quantity of solutiononthe -cellulosic material from about 60%; to about equal to. the weight of the materialitself, i; e: a:

' weight pick-up of about 60% to1.00.-%'.

In most prior art methods the materialimpregmated with the solution would be substantially immediately alkalized. with an alkalizing agent (without a partial drying step') thoroughly washed and dried.

By such prior art. procedures which do not in clude a partial drying, step. with this type of. solutionsfrom about 30% to 70% of. the'titanium values would be precipitated from solution; and

fall.to.the botton'rof theneu-tralizing tank. The

cellulosi'c: material processed: according tothese welleknown methods would exhibit relatively poor firezresistant characteristics and: would exhibit a; dusty and. chalky appearance. The fire retardeancy would be'poor at the onset and would-be diminished rapidly, upon repeated washing. and:

laundering of thecellulosic material.

partial drying step. should; be carried: out by ex.-

posing the: impregnated material. to the atmosphere for a short interval: of'time to; reduce by. evaporation the weight; of the solution held. by

,the cellul'osic material'to to' A; the amount picked up or impregnated in the cellulos-icmate rial.

It hasbeen foundithat the partialdrying.opera ation may be carried. out at roomtemperatureor temperatures up. to 60C. Obviously atelevated temperatures" less time is necessary to partially dry' this solution on. the material. Ithas, been found that 45' minutes'drying time" is necessary at room temperatures (temperatures underv atmospheric conditions). At 40 C. 35 minutes maybe employed while at 60 C. 10. minutes may be employed. During such partialdrying step-the solution is gel'atinized. on cellulosicimaterial form: ing a transparent. gel, and'substantiallyall' of the titanium values impregnated in the cloth are re tained in this gel formation.

. The cellulosic material containing the gelath nized treating agent is thensubj'ected to ail-alkalizing agent in order. to raise the pH of. the treated materialto'. above;7.5 preferablyacove. 9.0 but'notiexceeding about 12.0. Thertype of. alka lizing agent used is unimportant although weak alkalizing agents such as, for example, sodium carbonate or ammonium hydroxide or carbonate, are preferred. Small amounts of soluble silicates such. as; sodium. silicate: may" be. added with the neutralizing: or alkalizing agent if" desired. By such addition the treated cloth will possess better resistance to afterglow than treated otherwise.

The amount of soluble silicate should be that requiredltorgive from 0.2 to 1.5, preferably about 1.0% 'SiOr on the final treated material. Such soluble silicatescmay also be added to the material prior to impregnation with the solution of partially substituted chloride of tetravalent titaniumy on after the; neutralization step, but it is preferredv to. add the soluble silicate during the neutralization step. The material is then rinsed well with water, for example by decantation, in order "to remove the soluble salts therefrom and subsequently dried.

It has been found that the; preferred; amuunt of: impregnant on; the. final. material: (dry basis): is; about 6.0% to 9.10%; of the-weight of" thefibrous:

cellulosic material when the partiallysubstitutedii chloride of tetravalent; titanium: solution. is. usedi alone, whileabout 14% to 1*6-%is preferred whem the: solutioncontains antimony chloride:

The: entire process may beicarriedout: atroom; temperature" although ifdesired, temperaturesup to 60 0;.may be employed.

The exactnature of the. physicalandrchemical. changes that take place during this; proc,ess--. is. not completely understood. I-I-owever,v 13116550111: tion: of: partially substituted chloride of "tetravalentttitanimnis' apparently converted to; a trans parent:v gel during the; dryingoperation; This; transparent geliad'heres tenaciouslyto; thee/elm losiumateria'l: and is not removeclbysubsequentv washing; It may bezheldiintheporesaorbetween. the fibers of the cellulosicr material; maybeabr sorbed. or: adsorbed on. the" surface or' mayreact to some; extent with the cellulosic: material itself.

To illustratepreferred": embodiments of thisin vention;. the following examples are presented:

EXAMPLE: 1 A] basic; tetravalent titanium v chloride solutionv containing 200 grams-per liter antimony-chloride,-v 60 grams per liter of titanium and. 84 grarnsper liter of chloridesin addition to thechloride values of. the antimony chloride was used for. treating apiece of cotton cloth. The cloth was cotton twill weighing 8.2' ounces per square yard.

The cloth was immersed inthe, aqueous solution. of. basictitanium chloride for 2 /zminutes and was passedthrough a hand wringer. The operation was repeated a secondtime (immersed and wrung; again) to-obtainv good soaking The treated cloth was weighed andfound to contain a weight pick-up. of 10.0%, i. e. the solutionretainedintheclothweighed as much asthecloth itelf. The-treated cloth was thenpartially dried by exposingjthe cloth tothe atmosphere at room temperature for 2 hours. After the partial dryingstep theoloth was weighed again anditwas found that the weight of the solution on the-cloth had been decreased to 50% of the original weight pickup on the cloth. During the partial, drying operation the, solution, was gelatinized. on the cloth to-form a transparent gel. The gel-containing treated cloth, after the partial drying operation wasthen immersed for 5 minutesin a solution of sodium hydroxide containing. 200, grams. per liter NaOH to. alkalize. the. solution i retained: on, the. cloth. The pH of theretained solution held by the cloth was 9.5. The excess solution was squeezed out of the cloth by passing the cloth through a hand wringer. The cloth was then washed well with water until the retained solution had a pI-I of 8.0. The washed cloth was then thoroughly dried. The entire procedure was carried out at room temperature. The treated cloth was subjected to a standard flame test and the results are recorded in Table 1.

The standard flame test is called the 45 Microburner test and consists of exposing the smooth side of the fabric at an angle of 45 inch above the top of a burner. The flame, 1% inches in length, is played onto the fabric for 12 seconds. The afterflaming and afterglow data are recorded in seconds. The procedure and apparatus assembly has been developed by the Quartersame manner as that described in the control run in Example 1. The results are recorded in Table 1.

EXAMPLE 3 Table 1 Example lhl d ExampleZ B i ttExampllril3 d Basic titaniumc ori e as c ianiumc ori econand antimony chloride Tltamum chloride acetate taining soluble phosphates g Partial Partial 5 Not l -r- Drying Not Partially Drying Not Partially if tially Dried Step In Dried Step In- Dried Process eluded eluded Afterflame (sec) 0 18 8 completelyburned 10 completelyburned. Appearance not dusty. dusty... not dusty. dusty not clusty dusty. Percent Titanium Values 0 50...... 0 0 60.

Lost During Neutralization Step.

master Corps of the United States Army and is described by Robert W. Little, Major in Quartermaster Corps, in his book entitled Flameproofing Textile Fabrics on pages 117-119, Reinhold Publishing Corporation, 1947.

In order to compare the process of the instant invention with a process in which the partial drying step has been omitted the following description is presented:

Another piece of cloth of the type previously described was placed in the same basic titanium chloride solution until substantially 100" Weight pick-up was obtained. Within a few minutes after the immersion step had been completed, the impregnated cloth was neutralized without the partial drying step. Again the cloth was neutralized by immersing for 5 minutes in a solution of sodium hydroxide as described above. The neutralized cloth was then processed according to the above procedure. The cloth was then subjected to the standard flame test and the results are recorded in Table 1.

EXAMPLE 2 The procedure described in Example 1 was re" 5 peated using this titanium chloride acetate solution except the partial drying step was carried out at a temperature of 59 C. and the drying time was minutes. The results of the standard flame test on the treated cloth are recorded in Table 1.

Again in order to show a comparison between the process of the instant invention with a procedure which does not utilize a drying step, a cloth was'treated in the same solution in the It should be noted that the data presented in Table 1 shows the results after laundering. The laundering process was carried out in a tumbling chamber with 0.5% soap solution at 0.

While the examples illustrate the employment of titanium chloride acetate solution, this being the preferred titanium chloride acylate, solutions of titanium chloride formate and titanium chloride propionate may be employed with similar efiect. These compounds, however, are somewhat more expensive to produce and therefore not as economical as the acetate salt.

By the utilization of the process of this invention which includes the partial drying step, it has clearly been shown that the titanium values are fixed in the material in a form in which substantially no alteration in appearance or texture of the material is observed. It should be noted that by applying the process of the instant invention increased flame resistance is obtained with substantially no loss of the titanium and antimony values during processing. The process is economical to employ and simple to operate and decided improvements are obtained in the appearance, texture of the treated fabric in the flame resistant characteristics and in the utilization of substantially all of the titanium and antimony values.

While this invention has been described and iilustrated by the examples shown, it is not intended to be strictly limited thereto and other modifications and variations may be employed within the scope of the following claims.

We claim:

1. Method for imparting fire resistance to fibrous cellulosic material which comprises impregnating said material with a transparent aqueous solution of a substance selected from the group consisting of titanium oxychlorides, titanium chloride acylates selected from the group consisting of titanium chloride formate, titanium chloride acetate and titanium chloride propionate, and mixtures thereof, partially dry- 7, ingthes impregnatedlmaterial by evaporationum til from 50% to 75%. of; the, weight of saidsolwtion in said material is removed, thereby forming a transparent gel, alkalizing said gel in said material with an. aqueous alkaline solution, and

washing and drying said material, the resulting.

Mo -16 oi: saidaimnr ena-ted titanium substance.-. based on" the weightof the fibrous cellulosic-ma terial, is retained in said: material afterwashing;

and-drying. 5 IRENE M. PANI-K.

WILLIAM F. SUILIVAN.

References Cited in the file of this patent.

UNITED STATES PATENTS 10 Number Name Date 2,570,566 Lane et a1. Oct. 9,- 1951* OTHER REFERENCES American Dyestufi Reporter, vol. 39, N0. 16,

15 Titanium Compounds as Fire Resistant Agents for Fabrics, 1. M Panik et all, Aug; 7, 1950: 

1. METHOD FOR IMPARTING FIRE RESISTANCE TO FIBROUS CELLULOSIC MATERIAL WHICH COMPRISES IMPREGNATING SAID MATERIAL WITH A TRANSPARENT AQUEOUS SOLUTION OF A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF TITANIUM OXYCHLORIDES, TITANIUM CHLORIDE ACYLATES SELECTED FROM THE GROUP CONSISTING OF TITANIUM CHLORIDE FORMATE, TITANIUM CHLORIDE ACETATE AND TITANIUM CHLORIDE PROPIONATE, AND MIXTURES THEREOF, PARTIALLY DRYING THE IMPREGNATED MATERIAL BY EVAPORATION UNTIL FROM 50% TO 75% OF THE WEIGHT OF SAID SOLUTION IN SAID MATERIAL IS REMOVED, THEREBY FORMING A TRANSPARENT GEL, ALKALIZING SAID MATERIAL WITH AN AQUEOUS ALKALINE SOLUTION, AND WASHING AND DRYING SAID MATERIAL, THE RESULTING TITANIUM SUBSTANCE BEING RETAINED IN SAID MATERIAL IN THE FORM OF A WASH-FAST, STABLE, TRANSPARENT GEL-LIKE STRUCTURE. 